Weight in relation to the range of one battery

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DasDouble   100 kW

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Weight in relation to the range of one battery

Post by DasDouble » Feb 12 2017 7:45pm

Hi, I would like to know the relation between weight to range of a vehicle. I want to know following: If I have double the capacity = means double of the battery weight, if I then also have double the range, or not. Would be awesome if someone could explain this with the help of some math :)

Thanks
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Re: Weight in relation to the range of one battery

Post by Recumbent Bicycle Source » Feb 12 2017 9:04pm

No.

The weight of the Battery is not relevant. The Total AH of the battery is relevant. And the chemistry of the battery and cells used will determine the weight.

I have a Cellman 14S 14AH battery. It weighs about 11lbs. I get about 30 miles without pedaling on my bike which would be in the 250lb range with me on it. If I Doubled the CAPACITY of the Battery I would double the RANGE assuming the same Cells. So if I added another 11lb Battery of equal capacity the range would be doubled.

The little bit of weight difference would be negligible. At some point however adding more weight will in fact decrease range... but probably not to the point you should worry unless you plan on really loading up with gear or are doing a lot of riding where you would be doing a lot of climbing pulling more amps from your pack.
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Re: Weight in relation to the range of one battery

Post by amberwolf » Feb 13 2017 12:44am

The total vehicle+rider+etc weight *does* matter for range; the more stops/starts (or hills) you have, the more it matters.

If your battery is a large enough percentage of that total weigth, then doubling that weight would not double your range. The exact new range you'd get could probably be worked out with math, but it'd be easier (for me) to just test it.


If the battery is a tiny percentage of the total weight, then it doesnt' impact the doulbed range as much by doubling the battery weight.


I havent' range tested the "new" packs, but they weigh quite a lot (around 35lbs each, IIRC), which is probably a little less than 10% of the trike weight itself (not counting my 170-180lbs). Two of them would be almost 20% of that weight, which is definitely significant, and because of that would probably not double my range in stop/start traffic, though it might do it if I had no or few stops, riding on the flats.

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Re: Weight in relation to the range of one battery

Post by DasDouble » Feb 13 2017 10:20am

Recumbent Bicycle Source wrote:No.

The weight of the Battery is not relevant. The Total AH of the battery is relevant. And the chemistry of the battery and cells used will determine the weight.

I have a Cellman 14S 14AH battery. It weighs about 11lbs. I get about 30 miles without pedaling on my bike which would be in the 250lb range with me on it. If I Doubled the CAPACITY of the Battery I would double the RANGE assuming the same Cells. So if I added another 11lb Battery of equal capacity the range would be doubled.

The little bit of weight difference would be negligible. At some point however adding more weight will in fact decrease range... but probably not to the point you should worry unless you plan on really loading up with gear or are doing a lot of riding where you would be doing a lot of climbing pulling more amps from your pack.
I think you have unerstood my question incorrect. I wantet know if the weight of twize the amount of a battery (which could result in twize the amount of ah / capacity) impacts in the total range of a bike / how much it impacts the total range of a bike because of the added weight.
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Re: Weight in relation to the range of one battery

Post by FluxZoom » Feb 13 2017 10:48am

There are simulators out there that may help you understand how weight influences range and power consumption.

http://www.ebikes.ca/tools/simulator.html This is an example of this. You can change lots of different settings to get a solid idea on how this works out. The weight does play a role, especially, as noted, when accelerating or going up an incline.

http://www.ebikes.ca/tools/trip-simulator.html Not sure but maybe this one may help as well.

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Re: Weight in relation to the range of one battery

Post by Schlafmutze » Feb 13 2017 12:23pm

It all depends on how much battery you already have to begin with, if say the battery is only 5% of the whole weight of your bike and yourself, making the battery twice as large thus making it 10% of total weight would in fact double the range.
One thing to keep in mind though that under normal usage conditions your twice as large pack will provide over twice as much total effective Wh due to each cell being loaded less, less voltage drop, less wasted ah and so on.
This would probably negate the extra weight with ease.

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Re: Weight in relation to the range of one battery

Post by amberwolf » Feb 13 2017 2:36pm

DasDouble wrote:I think you have unerstood my question incorrect. I wantet know if the weight of twize the amount of a battery (which could result in twize the amount of ah / capacity) impacts in the total range of a bike / how much it impacts the total range of a bike because of the added weight.
Hopefully you read my answer to you, because it gives you as much of an answer as there is, without what would probably be some complex math. I'm not the best person to give math answers, just practical experience.


But the basic answer is still: it depends on the proportion of battery weight to the rest of the vehicle/rider/cargo, *and* the number of stops/starts and/or hills (including their slope and length).

All of those will determine how much range difference there will be with a change in battery weight/capacity.


It is still more complex than that, though:

One other thing that will make some difference is also the original capability of the battery to deliver current without sagging in voltage, *and* how much difference doubling the capacity of the battery would make to that.

One example: If there is a lot of sag under load, and there's a lot of load time during a ride, you'll get less capacity out of the pack than you'd expect based on simple capacity ratings. Plus as it gets lower in capacity, the BMS (if any) will start cutting out because of LVC as the voltage sags, even though there's still "plenty" of juice left in the cells (if they were being used at a lesser load).

But adding a second identical pack would probably decrease that sag by a lot, possibly to less than half the amount it had been, simply because there is less load on all the cells now. This would then add more range to the vehicle, but how much more depends on the battery itself (cell type, BMS LVC, etc), as well as all the other things I listed before.


There's probably other factors I dont' recall ATM.

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Re: Weight in relation to the range of one battery

Post by docw009 » Feb 13 2017 5:49pm

Let's consider my Luna mini. It's 14Sx2P for 28 cells and weighs 3 pounds. I have a light weight bike at 29 pounds with motor, and I am 190. Total weight is 222 pounds, so a 3 pound battery is 1.3% of the total. I could buy a 3 pound sack of potatoes, and it would have little effect on range. Potatoes don't have many watt-hours. That's where you need your math.

My battery is about 6 amp-hr, and 52 volts, which rounds off to 300 watt-hour, which I will derate by 20% to 240 watt-hr, (because vendors stretch their numbers.) At my slow riding speeds, I only use 10 watt-hr/mile, so I could go 24 miles. You might go faster and use 20 watt-hr/mile, so you get 12 miles.

If I had a second Luna Mini, I double the weight, but that don't matter. I'm doubling the watt hours. Math says 48 miles is possible. You get 24 miles. In any case, 2X the range, whatever it is, is to be expected.

By the way, you can make a battery out of a potato. Runs a digital watch.

Also, if you are thinking about acceleration and performance, sure, more weight hurts performance, and if you were doing a economy test, you would see where 3 extra pounds would use more watt hours if we counted them all up on a 1000 mile competition. Ain't going to matter when you ride 15-20 miles and recharge,

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Re: Weight in relation to the range of one battery

Post by DasDouble » Feb 13 2017 7:04pm

amberwolf wrote:
DasDouble wrote:I think you have unerstood my question incorrect. I wantet know if the weight of twize the amount of a battery (which could result in twize the amount of ah / capacity) impacts in the total range of a bike / how much it impacts the total range of a bike because of the added weight.
Hopefully you read my answer to you, because it gives you as much of an answer as there is, without what would probably be some complex math. I'm not the best person to give math answers, just practical experience.


But the basic answer is still: it depends on the proportion of battery weight to the rest of the vehicle/rider/cargo, *and* the number of stops/starts and/or hills (including their slope and length).

All of those will determine how much range difference there will be with a change in battery weight/capacity.


It is still more complex than that, though:

One other thing that will make some difference is also the original capability of the battery to deliver current without sagging in voltage, *and* how much difference doubling the capacity of the battery would make to that.

One example: If there is a lot of sag under load, and there's a lot of load time during a ride, you'll get less capacity out of the pack than you'd expect based on simple capacity ratings. Plus as it gets lower in capacity, the BMS (if any) will start cutting out because of LVC as the voltage sags, even though there's still "plenty" of juice left in the cells (if they were being used at a lesser load).

But adding a second identical pack would probably decrease that sag by a lot, possibly to less than half the amount it had been, simply because there is less load on all the cells now. This would then add more range to the vehicle, but how much more depends on the battery itself (cell type, BMS LVC, etc), as well as all the other things I listed before.


There's probably other factors I dont' recall ATM.
Hey, that´s something which I have never consideret about before. Before I have read your post, I have always thought duo the high temperature which gets produced when using much amps, it is always better to go as high with voltage as possible when building a battery.. But I have never thought about the voltage sag when having the batterys under high load.
#You never stop learning :lol:
docw009 wrote:Let's consider my Luna mini. It's 14Sx2P for 28 cells and weighs 3 pounds. I have a light weight bike at 29 pounds with motor, and I am 190. Total weight is 222 pounds, so a 3 pound battery is 1.3% of the total. I could buy a 3 pound sack of potatoes, and it would have little effect on range. Potatoes don't have many watt-hours. That's where you need your math.
When I have asked for some math, I have thought about something like on one of my old theareds, where I have talked about the highest, possible speed you can get, on a special amount of power like this:

"P(Motor)=((A/2 x CW x D x v³)+(Cr x m x g x v)) x 1,11"

https://endless-sphere.com/forums/viewt ... =3&t=75005
docw009 wrote:By the way, you can make a battery out of a potato. Runs a digital watch.

Also, if you are thinking about acceleration and performance, sure, more weight hurts performance, and if you were doing a economy test, you would see where 3 extra pounds would use more watt hours if we counted them all up on a 1000 mile competition. Ain't going to matter when you ride 15-20 miles and recharge,
Hahaha, I knew that experiement with potatos before :lol: .. You can also do it with many other things which are originally made to end in your mouth and not in for example an ebike, like a watermelon etc :wink:
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Re: Weight in relation to the range of one battery

Post by ferret » Feb 14 2017 8:18am

For riding on flat ground at constant speed, weight has negligible effect on range.
When accelerating or riding uphill, performance is inversely effected by total (battery+bike+rider) weight. For example if you get raise the total weight by 10% you will reduce accelerating and climbing performance by 10%. How much will this reduce the range depends on how much you accelerate and climb during the ride.

Hope this helps,
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Re: Weight in relation to the range of one battery

Post by DasDouble » Feb 14 2017 9:44am

ferret wrote:For riding on flat ground at constant speed, weight has negligible effect on range.
When accelerating or riding uphill, performance is inversely effected by total (battery+bike+rider) weight. For example if you get raise the total weight by 10% you will reduce accelerating and climbing performance by 10%. How much will this reduce the range depends on how much you accelerate and climb during the ride.

Hope this helps,
Avner.
Helped a lot! Thanks! :D
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